Roof Timber Sizes And Spans

Maximum rafter spans for a patio roof in areas with mild climates patio roofs are generally designed for loads of 30 psf pounds per square foot.

Roof timber sizes and spans.

All figures are based on normal loading conditions found in domestic construction. For pitched roofs flat roofs and ceiling joists. Surveyors and structural engineers utilise data from tables below to help calculate the correct size strength and centres of roof timbers for the required spans and loadings. This span table is to the format and methodology given in bs 5268 7 2.

Click on a span to generate a full calculation you can adjust the exact span. Ceiling joist span use this table to determine the maximum lengths of ceiling joists based on species of lumber joist spacing and joist size. Find the column for your dead load and spacing and the row for your timber size to find the permissible clear span in metres. These spans were calculated using our flat roof joist calculation.

All the figures are based on roofing tiles or slates laid on timber laths over sarking felt. The following tables give details of the allowable spans and spacing for some of the more common timber sizes used in flat roof construction. In any other situation you should refer to trada document span tables for solid timber members in floors. Surveyors span tables for designing roof rafters.

The following tables give details of the allowable spans and spacing for some of the more common timber sizes used in traditional roofing construction.